Is Environmental Sampling Sufficient for Food Safety?

In October 2019, the Food Safety and Operating Committee of the Innovation Center for U.S. Dairy published its updated environmental Pathogen Control Guidance Document, a comprehensive document intended to help the U.S. dairy industry control pathogens in wet and dry dairy processing environments (available at usdairy.com/foodsafety). In its guidance document, the Innovation Center details five principles that should be followed to ensure effective pathogen control. These include:

1. Separate raw from ready-to-eat (RTE);
2. Follow Good Manufacturing Practices (GMPs);
3. Institute sanitary facility and equipment design;
4. Implement effective cleaning and sani­tation procedures and controls; and
5. Initiate environmental pathogen monitoring.

These principles are in keeping with a 2022 systematic literature review showing that 10 of the 12 (83%) foodborne illness outbreaks involving pasteurized dairy products from 2007 to 2021 were due to contamination with Listeria, an environmental contaminant (Can J Pub Health. 2022;113:569-578). A similar study that looked at reported outbreaks from 1998 to 2011 coming from both pasteurized and unpasteurized cheese showed that, in 44 outbreaks stemming from cheese made with pasteurized milk, 24% were attributed to Listeria and the remainder were a mix of Salmonella, Campylobacter, Bacillus, E. coli, and others, all considered environmental contaminants (Foodborne Pathog Dis. 2014;11:545-551). The importance of focusing on the five principles of pathogen control is very clear.

One Step Further

But within the realm of environmental monitoring, is the vitally important task of environmental sampling to control pathogens enough? Will a good pathogen environmental monitoring program (PEMP) sufficiently and consistently ensure product safety and a high level of product quality? According to Neil Bogart, a highly regarded expert in dairy safety and the president of Bogart Food Safety and Sanitation Associates, Inc., an Alabaster, Ala.-based food safety and sanitation advisory firm with a primary focus on dairy processing, the answer is, “Perhaps not.”

“While swabbing, [adenosine triphosphate] ATP surface monitoring, and other environmental sampling methods are crucial steps for controlling widespread pathogens,” says Bogart, “they do not provide the complete picture in wet milk processing. Thermoduric organisms, for instance, can carry over from the raw milk supply, or pockets of contamination can become established in processing equipment where swabbing is impractical. This underscores the necessity of a robust process monitoring program to fully validate sanitation procedures and pinpoint contamination hotspots that can significantly impact quality and safety.”

When considering a process monitoring program for cheese and dairy powder processing, for example, emphasis must be placed on spore-forming bacteria due to their ability to survive extreme processing conditions, their potential pathogenicity, and because they possess strong spoilage capacities, which could lead to proteolysis, lipolysis, gas formation, and other quality defects. These bacteria can originate from the soil, feces, bedding, feed, or milking equipment but can also enter the milk via contaminated teats, milking cups, bulk tanks, or transport tankers. Pockets of contamination can also develop within the processing plant due to failures in milk handling, sanitation, or preventive maintenance. Extended production run times exacerbate the problem. Endospores formed by these organisms may survive pasteurization and subsequently germinate into vegetative cells that may be psychrotolerant but prefer to grow in warm conditions, giving them an even greater chance to contaminate many dairy processing environments (Front Micro. 2017;8:1-15).

Sporeformers of primary concern to dairy processors are members of the genera Bacillus and Clostridium; however, except in certain cheese processing, concern over the anaerobic Clostridium is often less than that for their aerobic counterparts. While many sporeformers are not pathogenic and are seen primarily as indicators of hygiene during milk collection, transport, or processing, certain members of these genera are well-known pathogens and, therefore, worrying from a food safety standpoint.